Electric motor brush assembly

ABSTRACT

An electrically conductive brush box is located against the upper surface of a base and has crimping tabs located against an oppositely disposed crimping surface. The base is formed of high temperature resistant plastic. A field case housing has a seat with a retention member adapted to retain the base against the seat. A screw is threaded into the field case housing such that the head presses against a surface of the base member to retain the base member in the seat. The screw member is located in non-contacting relationship with the electrically conductive brush box. A spacer member is adapted to space the portion of the crimping tab against the crimping surface away from the field case housing. The brush box includes a biasing member holder and the crimping tabs are located adjacent the holder.

FIELD OF THE INVENTION

The present invention relates to electric motors; and more particularly,to the brush assembly of electric motors.

BACKGROUND OF THE INVENTION

Electric motors are used in a variety of applications, including powertools. Such electric motors typically include a motor shaft, a motorarmature, magnets, a fan baffle, a commutator assembly, brushes andelectrical leads. The electrical leads selectively link brushes to apower source. The motor armature is fixed for rotation with the motorshaft and a series of copper conducting wires are wound in variouspatterns about peripheral slots. Ends of the wires are fused to thecommutator. The commutator is fixed for rotation with the motor shaftand provides an electrical connection between the rotating armature andthe stationary brushes.

The brush is often held in place by an electrically conductive brushbox. The electrical current powering the motor flows through thiselectrically conductive brush box through the brushes and into thecommutator. As a result, the temperature of the brush box (which istypically made of brass) can be raised to fairly high levels;particularly when high amperage applications are concerned like batteryoperated power tools. As such, the temperature of the brush box can besufficient to potentially damage the field case housing. Thus, it isdesirable to minimize any such risk of damage.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, an electricmotor brush assembly is provided. The assembly includes an electricallyconductive brush box and at least one crimping tab. A base member has anupper surface and an oppositely disposed crimping surface. Theelectrically conductive brush box is located against the upper surfaceand has a portion of the crimping tab located against the oppositelydisposed crimping surface. A field case housing has a seat with aretention member adapted to retain the base against the seat. A spacermember is adapted to space the portion of the crimping tab against thecrimping surface away from the field case housing.

In accordance with another aspect of the present invention, an electricmotor brush assembly with an electrically conductive brush box, abiasing member holder, and at least one crimping tab adjacent thebiasing member holder is provided. A base member has an upper surfaceand an oppositely disposed crimping surface. The electrically conductivebrush box is located against the upper surface and has a portion of thecrimping tab located against the oppositely disposed crimping surface. Afield case housing is adapted to retain the base member.

In accordance with one aspect of the present invention, an electricmotor brush assembly with an electrically conductive brush box adaptedto hold a brush and having at least one crimping tab is provided. A basemember is formed of high temperature resistant plastic and is adapted tocooperate with the crimping tab to retain the brush box against asurface of the base member. A field case housing has a seat and the basemember is located against the seat. A screw member has a head and isthreaded into the field case housing such that the head presses againsta surface of the base member to retain the base member in the seat. Thescrew member is located in non-contacting relationship with theelectrically conductive brush box.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is an expanded perspective view of a preferred motor assemblyaccording to the present invention;

FIG. 2 is a cross-sectional view of the field case housing of FIG. 1;

FIG. 3 is a cross-sectional view similar to FIG. 2, but includingadditional components of the field case housing sub-assembly;

FIG. 4 is a perspective view of the cover plate sub-assembly;

FIG. 5 is a cross sectional view taken along line 5—5 of FIG. 4;

FIG. 6 is a perspective view similar to FIG. 4, showing the fieldhousing subassembly and cover plate subassembly assembled together;

FIG. 7, is a partial cross sectional diagrammatic view of the coverplate assembled to a tool;

FIG. 8 is a fragmentary perspective view of the field case housing withthe brush assembly attached thereto;

FIG. 9 is an expanded plan view of a preferred brush assembly;

FIG. 10 is a perspective view of the assembled brush assembly of FIG. 9;

FIG. 11 is a bottom plan view of the assembled brush assembly of FIG.10; and

FIG. 12 is a perspective view showing the brush assembly being attachedto the field case housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. For example, although the motor is illustratedand discussed herein in terms of its use in association with a powertool, the motor may also be used for various other applications.

Referring to FIG. 1, a preferred embodiment of a motor 10 according tothe present invention is illustrated. Motor 10 includes a field casehousing 12, brush assemblies 14, motor can 16, baffle 18, armature 20,commutator 22, shaft 24, end plate 26 and front 27 and rear 28 bearings.Housing 12 is preferably molded as a single, integral part and includesa generally cylindrical flange 30. Flange 30, however, includes ashorter, elongated, linear, straight edge 32 (or short flat spot) and alonger, elongated, linear, straight edge 34 (or long flat spot).

Referring to FIG. 1 and FIG. 2, field case housing 12 is a generallytubular body. In molding housing 12, it is desirable to reduce warpingduring cooling of the thermoplastic material. This facilitates propermotor can 16 alignment with bearing 28 (and in turn, with shaft 24 andarmature 20). Housing 12, therefore, has walls with a substantiallyconstant thickness wherever possible. For example, housing 12 includes acorresponding flat spot 13 aligned with longer flat spot 34 of flange30. The inside of housing 12 also has the corresponding flat spot 13 tomaintain the constant wall thickness. Preferably, the substantiallyconstant wall thickness varies by less than about fifteen percent; andmore preferably, by less than about five percent. Further, it ispreferred that field case housing 12 has the substantially constant wallthickness over at least about 85 percent of its (in this case excludingthe thickened bosses on the flange, the locating ribs, and the conicalscrew insertion segment) surface area; more preferably, at least about90 percent; and even more preferably, at least about 95 percent.

In order to strengthen the flange 30, a series of radial-aligned flangereinforcing ribs 35 (seen best in FIG. 6) are located between flange 30and the adjacent wall segment of housing 12. In addition, flange 30includes thickened reinforcing bosses 37 (seen best in FIG. 6) aroundthe plurality of a apertures 33 which are used in attaching flange 30 offield case housing 12 to end plate 26. At the end of housing 12 oppositeflange 30, a conical end segment 41 is provided. The inner surface 39 ofthe end segment 41 has a conical shape leading to a rear bearing cavity29 adapted to receive and retain rear bearing 28. The walls at thedistal end of the conical segment are slightly thickened to providesupport for rear bearing 28. A series of radially-aligned end segmentreinforcing ribs 43 are also included. In addition, several ofradially-aligned end segment stabilizer ribs 43 include slot 45 whichprovides a wire trap adapted to retain an electrical wire. It ispreferred that flange reinforcing ribs 35 and end segment reinforcingribs 43 have a thickness corresponding to about 75% of the substantiallyconstant wall thickness.

Inner surface 38 of housing 12 has a plurality of arcuate ribs 36 whichare molded to precise dimensions to accurately align motor can 16 abouta central axis of housing 12. The precision is provided by firstcreating the mold from which housing 12 is made with small arcuate ribs36 and iteratively increasing the thickness of the ribs 36 based uponmolding results, thereby accounting for any warping during injectionmolding. Ribs 36 are arcuate in that they match the outer curvature ofmotor can 16. The end of arcuate ribs 36 near the open end of thehousing 12 are of a different thickness. This thickness, however, hasalso been iteratively increased to cooperate with a member 64 (seen inFIG. 4) of end plate 26 to accurately locate housing 12 and end plate 26coaxially relative to each other. At its greatest dimension, the overallwall thickness of housing 12 at the arcuate alignment rib 36 ispreferably less than about two times the substantially constant wallthickness; and more preferably, less than about 1.5 times. Inner surface38 also includes an alignment rib 40 which cooperates with acorresponding alignment recess 42 on motor can 16 to rotationally alignmotor can 16 within housing 12.

Referring to FIG. 3, housing 12, motor can 16, and fan baffle 18 areillustrated assembled together. Notches 44 in motor can 16 cooperatewith tabs 46 extending from fan baffle 18 to align these two componentstogether (seen best in FIG. 1). This also serves to align baffle 18 withhousing 12, since motor can 16 and housing 12 are aligned as a result ofthe alignment rib 40 and cooperating recess 42. Housing 12 includes twoscrew insertion apertures 48 associated with cylindrical guide member 50which cooperate with corresponding screw receiving apertures 52associated with conical guide members 54 of fan baffle 18.

Preferably, each screw insertion aperture 48 of housing 12 includes anelongated cylindrical segment 50 operating as a cylindrical guidemember. In addition, each screw receiving aperture 52 of baffle 18preferably includes a conical segment 54 at its receiving end operatingas a conical guide member, thereby providing an enlarged diameteropening at the outer origin of aperture 52. The elongated cylindricalsegment 50 is adapted to guide a tip of screw 58 passing therethroughand into the conical segment 54, even when motor can 16 is magnetized bymagnets 56. Similarly, the diameter and slope of the conical segment 54is adapted to receive a distal end of screw 58 passing through the screwinsertion aperture 48 and guide it down into the screw receivingaperture 52, even when motor can 18 is magnetized. Preferably, thediameter of the conical segment at its outer end is at least about twotimes the diameter of the insertion aperture 48; and more preferably, atleast about 2.5 times the diameter of the insertion aperture 48.

With continuing reference to FIG. 3, both of the cylindrical guidemembers 50 and the conical guide members 54 have a segment that extendsaway from the wall of the corresponding part (housing 12 and baffle 18,respectively). In addition, each of these extending segments is apartial cylindrical wall segment that is bound on one side by the innersurface of motor can 16. Thus, these extension segments cooperate withthe inner surface of motor can 16 to guide and receive screw 58 asdiscussed above. In addition, the receiving screw aperture 52 is adaptedto provide a portion into which the threads of screw 58 self-tap.

In addition to conical guide member 54 and its associated screwreceiving aperture 52, baffle 18 includes a transverse wall 53 with anaperture 55 therethrough. In addition, two opposing guide walls 57, eachaligned with one of the oppositely disposed magnets 56, extend at aninety degree angle from transverse wall 53 adjacent aperture 55. Guidewalls 57 are adapted to guide armature 20 past motor magnet 56 assemblywithout contacting and damaging the motor magnet 56 assembly. Guidewalls 57 preferably extend an axial length which is at least about 65percent of the distance from transverse wall 53 to an edge of the magnet56 assembly; and more preferably, at least about 75 percent. It is alsopreferred that guide walls 57 be adapted to prevent an axis of armature20 from deviating by more than about three degrees from the finalposition of armature 20 axis; and even more preferably, prevent fromdeviating by more than about two degrees. Additionally, guide walls 57and aperture 55, in combination with the conical inner surface of endsegment 41 of field case housing 12, is adapted to prevent any part ofarmature 20 from extending transversely toward a magnet 56 a distanceabout equal to or greater than the transverse distance between guidewall 57 and magnet 56. These guide walls are adjacent the aperture alongless than about 65 percent of the circumference of the aperture; andmore preferably, less than about 50 percent of the circumferenceaperture. Thus, air passages are left between the guide walls permittingair to pass to the fan.

Field case housing 12, motor can 16, and baffle 18 are assembledtogether as a field case housing sub-assembly using screws 58. Motor can16 includes a metal cylinder made using a powder metal process or usinga stamping or machining process. A motor magnet assembly includes motorcan 16 and two opposing magnets 56 adhesively mounted on the innersurface of motor can 16 with spaces therebetween. Motor can 16 has analignment recess 42 in its outer wall which cooperates with thealignment rib 40 on the inner surface 38 of field case housing 12. Motorcan 16 is rotably oriented by aligning the alignment rib 40 with therecess 42. Then motor can 16 is press-fit into field case housing 12where it is frictionally held due to the tight fit between the arcuateribs 36 and the outer surface of motor can 16.

Baffle 18 is then rotably oriented by aligning notches 44 in the end ofmotor can 16 with protrusions 46 of baffle 18. This also appropriatelyaligns the two screw insertion apertures 48 with the corresponding screwreceiving apertures 52. Screws 58 are passed through the cylindricalguide members 50 toward the conical guide members 54 and the distal endof the screw 58 is prevented from moving outside the diameter of thereceiving end of the conical segment 54 as discussed above. Screws 58are guided to the base of the conical segment 54 and into the smallerdiameter segment of the screw receiving aperture 52 where the threads ofthe screw 58 are driven into the surrounding material.

Referring to FIG. 4 and FIG. 5, end plate 26 has an outer raised ring 60and an inner raised ring 62. Inner ring 62 includes a precisely machinededge 64 that cooperates with the ends of the arcuate ribs 36 toaccurately align end plate 26 and housing 12 together. Rings 60, 62 areconnected to each other by a web 66 having four unequally spacedattachment bosses 68 associated with corresponding screw apertures 70.The surface of the bosses 68 are also precisely machined to aidalignment of field case housing 12 and end plate 26 together.

Web 66 has a plurality of raised reinforcing ribs 72 on its surface.Many of the reinforcing ribs 72 run radially between inner raised ring62 and outer raised ring 60. Two of the ribs 74, 76 run in a generallytangential direction, one is a longer, elongated, linear rib 74 and theother is a shorter, elongated, linear rib 76. In addition to providing areinforcing function, these elongated ribs 74, 76 provide visual indiciaas discussed below. In providing this visual alignment function, theseelongated ribs 74, 76 preferably extend along a distance of at leastabout 1.25 centimeters; and more preferably at least about 2.5centimeters. Reinforcing bosses 68 additionally reinforce web 66 aroundvarious screw apertures 70 which operate as attachment features. Each ofthese elements 64, 68, have a top surface in the same plane upon whichthe outer surface of flange 30 may rest when assembled to cover plate26.

An end plate sub-assembly is assembled as seen in FIGS. 4 and 5. Rearbearing 28 is press fit onto the rear end of the motor shaft 24 and thefront bearing 27 is press fit into a machined recess 78 surrounded by acylindrical wall 80 in the front side of end plate 26. Front bearing 27is also press-fit onto the front end of the motor shaft 24. Thepress-fit arrangements operate to frictionally hold these componentstogether as a sub-assembly during manufacturing.

Referring to FIG. 6, the field case housing subassembly and the endplate subassembly are next assembled together. Housing 12 is illustratedin a radially aligned position against end plate 26. The long elongatedmember 74 and the short elongated member 76 operate to provide indiciacapable of enabling proper rotary orientation of the parts 12, 26relative to each other using solely the visual indicia. Elongatedmembers 74, 76 are visually aligned with the flat spots 34 and 32,respectively, of flange 30. Thus, the subassemblies can be simply andeasily aligned to each other without the disadvantages associated withmechanically interacting alignment features.

It is preferred that the visual indicia be formed into surface of endplate 26 as illustrated. The term “visual alignment member,” as usedherein, however, includes, for example, printed markings or componentedges. Cooperating alignment members, however, excludes merely aligningtwo external edges of components together, particularly if the edges arenot elongated. The visual indicia is accurate enough to align apertures33 in flange 30 with cooperating apertures 70 in cover plate 26. Thus,based upon the visual alignment, a screw (not shown) may be passedthrough each set of aligned apertures 33, 70 to attach housing 12 andcover plate 26 together.

Referring to FIG. 7, the assembled motor 10 (represented by the shaft 24and armature 20) is illustrated as part of a tool 81. The tool includesa mating housing 82 which is attached to cover plate 26 using screws(not shown) through the outer set of apertures 84. The complete detailsof tool 81 and its components are not discussed herein as they arefamiliar to those skilled in the art. In general, motor shaft 24 rotatesa gear 86 which in turn, rotates a tool shaft 88 which is used toperform work on a workpiece. More importantly, the mating housing 82 oftool 81 includes a bearing retention shoulder 90 which operates toretain the front bearing 27 in place. The location of the front bearing27 between cover plate 26 and tool mating housing 82 is preferred forseveral reasons. For example, this location stabilizes motor shaft 24close to tool gear 86, reducing noise. Additionally, by trapping bearing27 between cover plate 26 of motor 10 and mating housing 82 of tool 81,no additional parts or machining is required (e.g., such as when alocking ring is used). Tool 81 may be, for example, a drill, areciprocating or circular saw, or some other tool.

Referring to FIG. 8, brush assemblies 14 are attached to the motor 10 toenable selectively providing electrical power to the motor 10. Brushassembly 14 includes a base 88, a brush box 90, a spring 92, a brush 94and an electrical connector 96. Base 88 is preferably formed of anon-metallic or non-electrically conductive material; more preferably,the material is a high melting temperature thermoplastic plastic orthermoset material; more preferably, the material is selected from thegroup of high temperature nylons, polyphenolyne sulfide (PPS) andpolyphthalamide; and even more preferably, the material ispolyphthalamide. In addition, the high melting temperature plasticpreferably has a melting point above about 280° C.; and more preferably,above about 310° C.

Referring to FIGS. 9, 10 and 11, base 88 is a generally planar elementwith retention members used to attach the brush box 90 to base 88. Thebrush box retention members include two arms 100 which form slots 104between themselves and the upper surface 102 of base 88. Slots 104 areadapted to receive opposing arms 106, 107 of brush box 90. Base 88retention members also include several recesses 108 to accommodatecrimping tabs 110 of brush box 90, as discussed hereinafter. Two of therecesses 108 include surfaces 112 which are oppositely disposed inrelation to upper surface 102 of base 88. Oppositely disposed surfaces112 are preferably parallel to the upper surface. Oppositely disposedsurfaces 112 provide a surface against which crimping tabs 110 may presswith a vector force component that is perpendicular to upper surface102.

Brush box 90 includes an open, tubular housing 114 with a rectangularcross-section. Brush box 90 is formed from a flat sheet of brassmaterial stamped into the correct shape and then folded to form brushbox 90. Brush box 90 has two opposing arms 106, 107, one extending fromeach side of housing 114. One of the two arms 107 and its associatedcrimping tab 111 is formed from material of a side wall of housing 114;thereby creating an opening 116 in the side wall. It is preferred thatat least one of the crimping tabs 111 is formed from material cut from aside wall of the housing 114.

The other side wall of the housing 114 includes a slot 118 foraccommodating the biasing member or spring 92. This opposing arm 106includes two crimping tabs 110 and a spring support member 120. Crimpingtabs 110 are located between the side wall with slot 118 and springsupport member 120 and adjacent thereto. This location provides addedstabilization to spring support member 120. Crimping tabs 110 aresufficiently long to reach around and rest against respective oppositelydisposed surfaces 112.

Assembly of brush box 90 to base 88 involves first sliding the opposingarms 106, 107 into slots 104 under cooperating arms 100 of base 88. Eachcrimping tab 110, 111 is crimped against base 88. Two crimping tabs 110adjacent spring support member 120 are crimped against surfaces 112located in recesses 108. Surface 112 is oppositely disposed to the uppersurface. Crimping tab 111 of the other opposing arm 107 is crimpedagainst a surface adjacent upper surface 102. This adjacent surface isalso located in a recess 108.

Returning to FIG. 8, brush 94 is located within housing 114. Brush 94includes an electrical shunt 96 or connector extending from a recess inbrush 94 to an electrical contact tab 124 to which it is welded orotherwise connected to provide electrical contact between brush 94 andbrush box 90. After assembly to field case housing 12 as discussedbelow, an electrical connector (not shown) is attached to the electricalconnector tab 126 to provide power from an electrical power source toand through brush box 90 to brush 94. A spring 92 is wound around thebiasing member support 120 adapted to bias a face of brush 94 which isarcuate and has a series of ribs against commutator 22.

Referring to FIG. 12, in addition to the brush box retention members 100and 108, base 88 includes retention members which, in connection withcooperating retention members on field case housing 12, attach base 88(and thus, brush assembly 14) to field case housing 12. Field casehousing 12 includes a seat 128 for brush assembly 14. Seat 128 includesa retention member in the form of a retaining hook 130. Hook 130provides a surface 132 or lip under which a cooperating portion of base88 is retained. The cooperating portion of base 88 includes the ledge134 (seen best in FIG. 9). Seat 128 also includes a snap lock 136 as asecond retention member also having a hook shape. After sliding theledge 134 under the retaining hook 130, the assembly 14 is rotateddownwardly. The snap-lock 136 is forced outwardly by the angled surface138 (seen in FIG. 11) of base 88 until it passes angled surface 138 andlatches against a cooperating portion of base 88. The cooperatingportion in this case is ledge 140 (seen in FIG. 9). Thus, retentionfeatures 134 and 140 on base 88 cooperate with retention features 130and 136, respectively, on field case housing 12 to attach brush assembly14 to the seat of field case housing 12.

As an alternative to or in addition to the snap-lock member 136, a screw142 may be provided in association with housing seat 128. Screw 142 isrotated into a recess of housing 12 until the head of screw 142 pressesagainst a cooperating portion of brush assembly 14. Preferably, screw142 does not come into contact with brass portions 90 of brush assembly14. By avoiding such contact, potentially damaging heat does not passthrough the screw 142 and into field case housing 12.

Similarly, crimping tabs 110 are preferably located a distance away fromfield case housing 12 by a spacer member. The spacer member is adaptedto space crimping tabs 110 away from field case housing 12. Asillustrated, the spacer member is the bottom surface 146 of base 88which is spaced away from crimping surface 112 and located against seat128 of field case housing 12. This is accomplished by locating crimpingsurface 112 within a recess 108 of base 88 away from bottom surface 146.Thus, the lower temperature thermoplastic material of housing 12 doesnot contact the heated metal of brush box 90. Of course, manyalternative spacer members are possible. For example, housing 12 mayinclude protrusions that extend up to base member 88 in areas away fromcrimping tabs 110, 111, or a completely separate component may beprovided between base member 88 and housing 12, which may be heatresistant.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

What is claimed is:
 1. An electric motor brush assembly, comprising: anelectrically conductive brush box having at least one crimping tab; abase member having an upper surface and an oppositely disposed crimpingsurface, the electrically conductive brush box being located against theupper surface and having a portion of the crimping tab located againstthe oppositely disposed crimping surface; a field case housing having aseat with a retention member adapted to retain the base against theseat; and said base member having a spacer member adapted to space theportion of the crimping tab located against the oppositely disposedcrimping surface away from the field case housing.
 2. An electric motorbrush assembly according to claim 1, wherein the base member comprises ahigh temperature thermoplastic material.
 3. An electric motor brushassembly according to claim 1, wherein the base member comprises athermoset material.
 4. An electric motor brush assembly according toclaim 1, further comprising a brush retained by the electricallyconductive brush box and electrically connected to a power supply, and abiasing member adapted to bias the brush against a commutator.
 5. Anelectric motor brush assembly according to claim 1, wherein theretention member comprises a lip under which a cooperating surface ofthe base is retained.
 6. An electric motor brush assembly according toclaim 1, wherein the retention member comprises cooperating snap-fitmembers on the field case housing and the base adapted to attach thebase and the housing together.
 7. An electric motor brush assemblyaccording to claim 1, wherein the retention member comprises a screw. 8.An electric motor brush assembly according to claim 1, wherein thespacer member is a surface of the base member which is spaced away fromthe oppositely disposed crimping surface and located against the fieldcase housing.
 9. An electric motor brush assembly according to claim 1,wherein the oppositely disposed crimping surface is located within arecess of the base member and wherein the oppositely disposed spacermember further comprises a wall of the base member surrounding therecess.
 10. An electric motor brush assembly according to claim 1,wherein the at least one crimping tab is a plurality of crimping tabs,and wherein the electrically conductive brush box further comprisesoppositely disposed arms, and at least one of the plurality of crimpingtabs extends off of each of the oppositely disposed arms.
 11. Anelectric motor brush assembly, comprising: an electrically conductivebrush box having at least one crimping tab; a base member having anupper surface and an oppositely disposed crimping surface, theelectrically conductive brush box being located against the uppersurface and having a portion of the crimping tab located against theoppositely disposed crimping surface; and a field case housing having aseat retaining the base member; wherein the field case housing and thebase member cooperate to maintain the at least one crimping tab awayfrom the field case housing.
 12. An electric motor brush assemblyaccording to claim 11, wherein the base member comprises a hightemperature thermoplastic material.
 13. An electric motor brush assemblyaccording to claim 11, wherein the base member comprises a thermosetmaterial.
 14. An electric motor brush assembly according to claim 11,wherein the electrically conductive brush box, biasing member holder andat least one crimping tab are made from a single, integral piece.
 15. Anelectric motor brush assembly according to claim 11, further comprisinga brush retained by the electrically conductive brush box andelectrically connected to a power supply, and a biasing member adaptedto bias the brush against a commutator.
 16. An electric motor brushassembly according to claim 11, wherein the seat comprises a lip underwhich a cooperating surface of the base member is retained.
 17. Anelectric motor brush assembly according to claim 11, further comprisingcooperating snap-fit members on the seat and the base member adapted toattach the base member and the seat together.
 18. An electric motorbrush assembly according to claim 11, wherein the retention membercomprises a screw.
 19. An electric motor brush assembly according toclaim 11, wherein the oppositely disposed crimping surface is locatedwithin a recess of the base member.
 20. An electric motor brush assemblyaccording to claim 11, wherein the at least one crimping tab is aplurality of crimping tabs, and wherein the electrically conductivebrush box further comprises oppositely disposed arms, and at least oneof the plurality of crimping tabs extends off of each of the oppositelydisposed arms.
 21. An electric motor brush assembly, comprising: anelectrically conductive brush box adapted to hold a brush and having atleast one crimping tab; a base member formed of high temperatureresistant plastic and adapted to cooperate with the crimping tab toretain the brush box against a surface of the base member; a field casehousing having a seat, the base member being located against the seat;and a screw member having a head and being threaded into the field casehousing such that the head presses against a surface of the base memberto retain the base member in the seat, the screw member being located innon-contacting relationship with the electrically conductive brush box.22. An electric motor brush assembly according to claim 21, wherein thebase member comprises a high temperature thermoplastic material.
 23. Anelectric motor brush assembly according to claim 21, wherein the basemember comprises a thermoset material.
 24. An electric motor brushassembly according to claim 21, further comprising a brush retainedwithin the housing and electrically connected to a power supply, and abiasing member associated with the assembly and adapted to bias thebrush against a commutator.
 25. An electric motor brush assemblyaccording to claim 21, wherein the seat comprises a lip under which acooperating surface of the base member is retained.
 26. An electricmotor brush assembly according to claim 21, further comprisingcooperating snap-fit members on the seat and the base member adapted toattach the base member and the housing seat together.
 27. An electricmotor brush assembly according to claim 21, wherein the at least onecrimping tab is a plurality of crimping tabs, and wherein the brush boxfurther comprises oppositely disposed arms extending from the housing,at least one of the plurality of crimping tabs extending off of each ofthe oppositely disposed arms.